Block-signal system.



L. A. HAWKINS.

BLOCK SIGNAL SYSTEM. v APPLICATION FILED JUNE 1. 1908.

Patented June 20, 1916 I KTTNESEEE;

ZN YENTUR LAURENCE A. HAWKINS. a

g. 5545 Wu UNITED STATES PATENT orrion I LAURENCE A. HAWKINS, OF SCI-IENECTADY, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE UNION SWITCH AND SIGNAL COMPANY, A CORPORATION OF PENN- SYLVANIA.

Specification of Letters Patent.

Patented June 20, 1916.

Application filed June i, 1908. Serial No. 435,861.

To all whom it may concern:

KINS, a citizen of the United States, resid ing at Schenectady, in the county of Sche formers to limit the current drawn from Be it known'that I, LAURENCE A. HAW

transformer when a train is standing diectly over 1ts secondary connections. These lmpedances may be either inductive nectady and State of New York,have inventor non-inductive.

ed certain new and useful Improvements in Block-Signal Systems, of which the follow ing is a specification. I

My invention relates to block signaling systems for electric railways having both track rails conductively continuous for all currents, and its object is to provide a novel signal system, which is reliable in operation, eflicient with respect to power consumption, unaffected by the power current in the rails, which defines the blocks with practically the same definiteness as though insulated joints were employed, and in which the amount of apparatus is reduced to a minimum.

I will describe one form of block signal system embodying my. invention and will then'point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing an electric railway having applied thereto. one form of block signal system embodying my invention.

Referring to the accompanying drawing, A represents the track rails of. an electric railway, which rails are conductively continuous for all currents, and B represents the third rail or supply conductor to which is connected one terminal of a power generator O. The other terminal of this generator may be connected to both track rails either directly or through a differential choke coil 0.

D represents an alternating current generator for the signal current, which may be of any suitable frequency. If the power current is direct, a 50 or 60 cycle generator is well adapted for supplying thesignal current. p

(1 represents the line wires transmitting the signal current from the generator D.

E E represent transformers having their primaries connected to line wires d and their secondaries connected at intervals across the track rails. These transformers thus act as sources of signaling current for the track rails. Impedances e and e are placed in series with the secondaries of these trans- G, G and G represent impedances which re connected across the rails at points beween the supply transformers and which may also-be either inductive or non-inductive. These impedances are not connected to directly opposite points on'the two rails, but

are connected to points which are displaced along the track a short distance, for instance, one hundred feet.

F, F, F and F represent track relays which are shown diagrammatically as of the well known two-phase induction type each comprising a short-circuited secondary f carrying the relay contacts, a winding supplied with current independently of the track circuits by its connection to the line wires (1 through a suitable phase controlling device indicated by the condenser f and a second winding f cooperating therewith to produce the relay torque. The windings f of two adjacent relays, as, for. instance, F and F are connected to overlapping rail lengths, as shown in the drawing. Since the amount of overlapmay be made anything desired by displacing the terminal connections of the impedance G the desired amount, each relay winding may be caused to span any desired length of rail, at the same time leaving it impossible for the car of no matter how short a wheel base to stand in a position in which neither relay F nor F will be deenergized.

The contacts of relays F and F are connected in series to control the circuit of the operating mechanism of the signal H, which circuit as here shown is supplied with'energy from the signal wires d. Similarly, the

relays F and F control the signal H for the succeeding block.

' The direction of traffic is from right to left, as indicated by the arrow. When the blocks are clear,'.the transformer E supplies alternating current to the track rails,which current flows in both directions from the transformer through the two impedances G and G, and the transformer E, similarly, supplies current to the rails of its block, its current flowing through impedances G and G The transformers E and E are similarly connected so that the currents from these two transformers flow through impedance G in parallel. The coil 7" of each relay has impressed on its terminals a voltage determined by the amount of current flowing and by the impedance of the short rail length in shunt to which it is connected. The length of rail spanned by each coil is determined by the torque desired in the relay and the amount and frequency of the signal current in the rails. I have found that with 7 4L to 5 amperes at cycles in the rails sufficient torque in the relay can be obtained for satisfactory operation with the length of rail spanned by each relay coil of not more tha one hundred feet. 7

As long as no trains are in the blocks, the relays are energized and the signals stand at clear. Furthermore, a train approaching a block has no effect on the relays except slightly to increase the torque of the relay at the entrance of the block by gradually shortcircuiting the track impedance G so as to draw a slightly increased current from the transformer E. As soon as the front wheels of the train, however, pass the first point to which the impedance G is connected, they begin to short-circuit the winding f of relay F, and as soon as the front wheels have covered the distance spanned by this relay coil, the relay is totally deenergized. The point at which the signal H goes to danger is consequently fixed within the short rail length spanned by the relay winding f. As

long as the train is between transformer E and relay F, relay F remains deenergized, while by the time the front wheels of the train have reached transformer E, relay F has been deenergized by the short-circuiting of the transformer; consequently, signal H stays at danger until the rear wheels of the train have passed over the short rail length spanned by the track winding of relay F. As soon as the rear wheels have passed the last point to which impedance G is connected, relay F has again reached its full torque, and, in fact, has a slightly increased torque due to the short-circuiting of impedance G and the somewhat greater current drawn from transformer E, so that signal H then returns to clear.

It will be seen that with a train in a' block, any current from an adjacent block that passes the impedance connected across the rails between the blocks, is in the reverse direction to that normally passing through the track winding of the relay of the block which is occupied so that its only effect is to Gopies oi thzls patent may be obtained for hold the relay more firmly in its denergized position.

With the arrangement which I have here shown, the length of rail to which each relay winding 7 is connected in shunt may be any desired Value, the only limit being the definiteness with which it is desired to fix the point at which the signal will go to danger. At the same time it is impossible for a car of no matter how short a wheel base to stand in a position in which neither relay F nor F will be de'e'nergized.

I do not desire to limit myself to the spe cific connections and arrangement of parts here shown, but aim in the appended claims to cover all modifications which are within the scope of my invention.

Having thus described my invention, what I claim is:

1. In a block signal system, in combination with an electric railway having both rails oonductively continuous for all currents, sources of alternating current connected across the rails at intervals, an impedance connected across the rails, at a point between two sources, the points on opposite rails to which the terminals of said impedance are connected being displaced from each other a short distance alongthe track and a pair of track relays connected in shunt to short over-lapping lengths of the two rails respectively, adjacent to, and on opposite sides of, the impedance, said rail lengths being alone suflicient to provide the necessary drop in potential for operatingthe relays.

2. In a block signal system, in combination with an electric railway having both rails conductively continuous for all currents, sources of alternating current connected across the rails at intervals, an impedance connected across the rails at a point between two sources, the points on opposite rails to which the terminals of said impedance are connected being displaced from each other a short-distance along the track, a pair of track relays connected in shunt to short over-lapping lengths of the two rails respectively adjacent to and on opposite sides of the impedance, said rail lengths being alone sufficient to'provide the necessary drop in potential for operating the relays, and a pair of signals controlled bysaid relays respectively.

- In witness whereof, I have hereunto set my hand this 28th day of May, 1908.

LAURENCE A. HAWKINS. Witnesses:

HELEN ORFORD, BENJAMIN B. HULL.

five cents each, by addressing the commissioner of Patents, Washington, D. G. 

